Method for quantitative evaluation of characteristics of micro-pore structure of deeply-buried high-pressure low-permeability sandstone reservoir stratum

Abstract

The invention discloses a method for quantitative evaluation of characteristics of a micro-pore structure of a deeply-buried high-pressure low-permeability sandstone reservoir stratum. The method comprises the following steps of: measuring the porosity and permeability of a standard rock core after oil washing and drying; vacuumizing a small rock sample cut from a plunger rock sample, and soaking the small rock sample in a mercury solution; injecting mercury into the rock core at a constant speed of 0.00005mL / min, and ending the experiment when the pressure reaches a highest value 900psi for a constant speed mercury injection apparatus; while the mercury is injected, performing real-time monitoring and automatic data acquisition and output by virtue of a computer; performing a high-pressure mercury injection experiment by using a standard plunger rock sample from a same stratum; and finally, taking a product of an efficiency of mercury ejection (EW) and the saturation degree of mercury ejection (SE) as a parameter index for classified evaluation of the micro-pore structure of the reservoir stratum, namely a comprehensive evaluation parameter E (E=EW*SE) of the micro-pore structure of the reservoir stratum, and judging the characteristics of the micro-pore structure according to distribution of E. According to the method disclosed by the invention, a relative accurate pore throat characteristic parameter is obtained by virtue of an experiment, and the defects of analysis with application of two mercury injection methods respectively are overcome.

Description

technical field [0001] The invention relates to the technical field of fine description of oil and gas reservoirs, in particular to a method for characterizing microscopic pore structure characteristics of deep high-pressure and low-permeability sandstone reservoirs. [0002] technical background [0003] Deep high-pressure low-permeability sandstone reservoirs belong to the category of low-permeability reservoirs, but they are different from conventional low-permeability reservoirs. Substantial changes in formation pressure during reservoir development lead to changes in pore structure and physical properties, which affect oilfield development results. Understanding the microscopic pore-throat characteristics of reservoirs is the key to developing this type of reservoirs. At present, mercury injection technology is still an important way to obtain the microscopic pore structure characteristics of reservoirs. In recent years, the constant-velocity mercury injection techniqu...

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Problems solved by technology

[0004] Existing researches mainly only use constant-speed mercury injection and high-pressure mercury injection tests, and the main problem is: the maximum mercury injection pressure of constant-speed mercury injection is low, so the minimum throat radius obtained by constant-speed mercury injection test is relatively large

High-pressure mercury injection studies the microscopic pore structure through the mercury injection pressure, the throat radius corresponding to the mercury injection pressure, and the pore-throat volume distribution controlled by a certain level of throat (the number of throats cannot be directly measured, and the pores and throats cannot be accurately distinguished).

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